1. Field of the Invention
The present invention relates to a steering device including a tilt/telescopic adjustment mechanism, with which a clamping condition during tilt/telescopic adjustment can be strengthened and rattling throughout the entire device can be prevented.
2. Description of the Related Art
In Japanese Patent Application Publication No. 2010-105662, a left/right pair of clamp members 8A, 8B molded from an aluminum alloy or a magnesium alloy using a die casting method are sandwiched to be capable of telescopic movement and tilting movement between inner peripheral surfaces 321A, 321B of left and right side plates 32A, 32B of an upper side vehicle body attachment bracket 3, and arc-shaped inner peripheral surfaces 82A, 82B formed on respective inner sides of the clamp members 8A, 8B surround and hold an outer periphery 11 of an outer column 1 (see (2) of FIG. 2 and FIG. 3 in Japanese Patent Application Publication No. 2010-105662).
Rectangular engagement projections 83A, 83B that are long in an axial direction are formed integrally with the arc-shaped inner peripheral surfaces 82A, 82B on a horizontal line passing through a center axis line of the outer column 1. Engagement recesses 12A, 12B are formed in the outer periphery 11 of the outer column 1 to penetrate an inner periphery 13, and the engagement projections 83A, 83B of the clamp members 8A, 8B are fitted into the engagement recesses 12A, 12B.
A cylindrical bush 22 molded using a material having a small frictional coefficient is fitted to the inner periphery 13 of the outer column 1, and the engagement projections 83A, 83B of the clamp members 8A, 8B are fitted into engagement recesses 23A, 23B formed in an outer periphery of the bush 22. An inner column 2 is fitted to an inner periphery of the bush 22 to be capable of sliding in the axial direction.
By engaging the engagement projections 83A, 83B with the engagement recesses 12A, 12B, 23A, 23B, the outer column 1 and the bush 22 are prevented from rotating relative to the clamp members 8A, 8B, and when a telescopic position of the outer column 1 is adjusted relative to the inner column 2, the outer column 1, clamp members 8A, 8B, and bush 22 are allowed to slide integrally in the axial direction.
Telescopic elongated grooves 81A, 81B that are long in the axial direction are formed below the clamp members 8A, 8B, and a clamping rod 34 is inserted into tilt elongated grooves 33A, 33B formed in the side plates 32A, 32B and the telescopic elongated grooves 81A, 81B. Slits 14, 24 are formed respectively in the outer column 1 and a lower surface of the bush 22, and when the clamp members 8A, 8B are clamped, the outer column 1 and the bush 22 are reduced in diameter such that the inner column 2 is held thereby.
Further, columnar engagement projections 84A, 84B, 84C are formed above and below the arc-shaped inner peripheral surface 82B of the clamp member 8B. The columnar engagement projections 84A, 84B, 84C are engaged with circular engagement recesses, not shown in the drawings, formed in the outer column 1, thereby fixing the clamp member 8B to the outer column 1 so that the outer column 1 is prevented from rotating (see (2) of FIG. 2 in Japanese Patent Application Publication No. 2010-105662).
Furthermore, engagement recesses 27A, 27B are formed in an outer periphery 25 of the inner column 2, and by bringing axial direction end portions of the rectangular engagement projections 83A, 83B that are formed on the inner periphery 13 of the outer column 1 to be long in the axial direction into contact with axial direction end portions of the engagement recesses 27A, 27B, the engaged components function as a stopper during telescopic adjustment (see FIGS. 4 and 5 in Japanese Patent Application Publication No. 2010-105662).
The outer periphery 25 of the inner column 2 is fitted to the inner periphery 13 of the outer column 1 to be capable of sliding in the axial direction, and the engagement projections 83A, 83B of the clamp members 8A, 8B are fitted into the engagement recesses 27A, 27B formed in the outer periphery 25 of the inner column 2. An axial direction length L1 of the engagement recesses 27A, 27B is set at a length obtained by adding a telescopic adjustment distance of the outer column 1 to an axial direction length L2 of the engagement projections 83A, 83B of the clamp members 8A, 8B.
By engaging the engagement projections 83A, 83B with the engagement recesses 12A, 12B, 27A, 27B, the outer column 1 and the inner column 2 are prevented from rotating relative to the clamp members 8A, 8B, and when the telescopic position of the outer column 1 is adjusted relative to the inner column 2, the outer column 1 and the clamp members 8A, 8B are allowed to slide integrally in the axial direction.
The following problems exist in Japanese Patent Application Publication No. 2010-105662. When an operating lever 349 is rotated, an interval between the side plates 32A, 32B narrows, causing the clamp members 8A, 8B to rotate such that a lower interval between the clamp members 8A, 8B narrows while an upper interval widens. As a result, the outer column 1 is clamped by the clamp members 8A, 8B unevenly, and therefore a stable clamping condition cannot be obtained.
To prevent the clamp members 8A, 8B from rotating, the engagement projections 83A, 83B are formed on the clamp members 8A, 8B and engaged with the engagement recesses 12A, 12B of the outer column 1 fixedly. With this configuration, however, dimension management is difficult, leading to an increase in cost. Moreover, when dimensional irregularities arise, rattling may occur, and therefore problems remain.
Further, the clamp members 8A, 8B are latched and fixed to the outer column 1 separately from the left and the right, and therefore the left and right clamp members 8A and 8B may rotate or twist differently during clamping, leading to a reduction in clamping force.
Furthermore, to prevent the clamp members 8A, 8B from rotating and twisting, the columnar engagement projections 84A, 84B, 84C formed respectively on the clamp members 8A, 8B are engaged with the circular engagement recesses, not shown in the drawings, formed in the outer column 1. As a result, however, increases in structural complexity and processing cost occur. Moreover, the outer column 1 and the clamp members 8A, 8B are provided as separate members, leading to an increase in a number of components.
Further, a stopper for use during a telescopic operation is formed by engaging the rectangular engagement projections 83A, 83B that are formed on the clamp members 8A, 8B to be long in the axial direction with the engagement recesses 27A, 27B formed in the inner column 2, and therefore the axial direction length of the engagement recesses 27A, 27B must be set at a length obtained by adding the telescopic adjustment distance to the axial direction length of the engagement projections 83A, 83B. As a result, the length of the inner column 2 also increases, leading to an increase in the overall size of the steering device.